This happens all over the place, including serious enough leaks that can cause explosions. Occasionally you hear about a building/house/etc blowing up because gas has leaked in from a line out front, or was run under a building, or something else. The only solution is checking, that and running new pipe. In my area back about 15 years ago Union Gas replaced all of the old turn of the century cast iron pipe with plastic. There was no shortage of the old stuff cracking and having developed leaks over the last 100 years. And of course, they checked every house along the way to the meter and if need be they dug up your front yard and replaced the pipe.

I'm actually not sure why the whistleblower thing is "needed" being that anyone who went to highschool(at least in Canada), knows that this is an issue. And yet, we have NG all over the place, or propane if you're too far off the line, or oil. And of course there's still plenty of people who don't have any of those, and are pure electric or wood.

Back when I lived in DC (late 1990s) there were regular reports of exploding manholes... with the best guess of the cause being a combination of gas leaks and electrical shorts. Of couse, in the report on the problem [goodspeedupdate.com] blamed PEPCO (electrical) not Washington Gas.

About 10 years ago, they had a solution -- install manholes with vent holes in them, so the gas pressure can't build up as easily. Of course, you instead get extra water underground, which can lead to faster corrosion of pipes.

Having a large accident would be a large liability for an energy company, and they would naturally take steps to avoid it.

That's not how regulated utilities work [1]. Their rates are set to guarantee a defined return on investment. To avoid having them "invest" in gold-plated executive toilets at Corporate Headquarters, the utility commission gets to decide what the company can invest in. If they approve an upgrade to the pipes, the Corporation gets to charge the customers for the cost plus ROI. If the Commission denies the request (to keep rates down) the liability is a business expense and the Corporation gets to charge the customers and add ROI to that, too.

Private or public, utility infrastructure is a political decision.

[1] City gas is a so-called "natural monopoly." Think about what an unregulated one would be like.